1. Field
A thin film magnetic head in which the surfaces of a read head and a write head facing a recording medium protrude toward the recording medium by means of thermal expansion is provided.
2. Related Art
Japanese Unexamined Patent Application Publication Nos. 2005-11413, 2005-11414, and 2003-168274 (Patent Documents 1 to 3) each propose a thin film magnetic head that includes a heating element provided therein and in which the magnetic gap and its vicinity are thermally expanded and the surface facing a recording medium is allowed to protrude toward the recording medium so that the floating height of the thin film magnetic head can be decreased. Japanese Unexamined Patent Application Publication No. 10-261248 (Patent Document 4) also discloses a related technique.
In order to appropriately control the amount of heat from the heating element, it is important to suppress the occurrence of electromigration in the heating element and to reduce the temperature dependency of the rate of change in resistance of the heating element. The temperature coefficient of resistance (TCR) can be obtained from the change in resistance with temperature, and the term “to reduce the temperature dependency of the rate of change in resistance” means to decrease the absolute value of the temperature coefficient of resistance (TCR).
The patent documents described above do not mention measures against electromigration and the temperature coefficient of resistance (TCR).
The electromigration easily occurs when current is applied to the heating element continuously for a long period of time. The occurrence of the electromigration markedly varies the resistance of the heating element. When the temperature dependency of the rate of change in resistance is large, the resistance of the heating element is markedly changed by the change in environmental temperature.
If the resistance of the heating element is markedly changed due to the current application time, environmental temperature, and the like, the amount of heat generated from the heating element markedly varies. Consequently, the amounts of thermal expansion of the magnetic gap, the core layer, and the like vary, resulting in an increase in the fluctuation in the amount of protrusion of the surface facing the recording medium. Such a fluctuation in the amount of protrusion is likely to increase the fluctuation in the write efficiency and read efficiency of the thin film magnetic head. In the worst case, if the amount of protrusion of the surface facing the recording medium becomes excessively large, the thin film magnetic head is likely to collide with the recording medium.